The present invention relates to a data transfer control device, an electronic instrument, and a data transfer control method.
The universal serial bus (USB) is known in the art as a serial bus interface for connecting a host, such as a personal computer, and peripheral devices. A lot of attention has been paid to the settling on USB 2.0 as a standard that enables the implementation of fast transfer speeds of 480 Mbps (HS mode), while maintaining compatibility with the existing USB 1.1 standard (refer to Japanese Patent Laid-Open No. 2002-135132).
USB differs from IEEE 1394 in that the host has the initiative for data transfer. In other words, the side that issues a transaction for data transfer is the host and a large part of control relating to the data transfer is done by the host. When exchanging data between USB devices (peripheral devices), therefore, it is necessary to provide a personal computer and connect those USB devices to that personal computer. For that reason, it is difficult to transfer data between USB devices in a peer-to-peer fashion.
With this IEEE 1394, IPover1394 is defined as a protocol for implementing the Internet protocol (IP) on an IEEE 1394 bus. This IPover1394 makes it possible to transfer an IP packet obtained by attaching a transmission control protocol (TCP) header and Internet protocol (IP) header to application data, thus enabling the implementation of a local area network (LAN) using IEEE 1394.
With USB, however, there is a technical problem in that a USB device cannot be made to operate as a LAN node (IP node), regardless of whether a protocol such as IPover1394 is defined.